I'm less interested in whether it's in an apps drawer than whether it will be started (e.g. if the frozen app is registered for an intent that fires off when GPS location changes, will it STILL fire off on GPS location change until you reboot?
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DVKFeb 7 '12 at 19:17

If the app you freeze is sending the intent, then no the intent will no longer happen. But if the app is receiving intents, then yes it should still receive them.
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ChillieFeb 7 '12 at 19:27

Freezing an app is similar to uninstalling it, in that it won't be able to run (whether by the user wanting to load it or via any intents). However, since it is frozen and not actually uninstalled, it does still take up space.

If you freeze a system app, you may have to reboot your phone. This usually isn't needed, but sometimes your home screen app may have a problem with a system app missing. Whether or not you reboot, though, the system app is frozen and will not be able to run.

If that were so, I wonder why some apps, while frozen, still show active processes -- even after a reboot. I guess the explanation is given by Chillie's comments on his answer, that a frozen app still is able to receive broadcasts.
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IzzyMar 10 '13 at 23:21